Haliclona : Skeletal System

Abstract

Sponge mesenchymal cells secrete and organize the mineral and the organic skeleton (collagen) according to its phylogenetic lineage. Haliclona spicules are siliceous oxeas, smooth, fusiform, and slightly curved, with acerate or hastate tips. The ectosomal skeleton is easily detachable, formed by a slightly disorganized tangential reticulation of oxeas. It is isotropic, predominantly paucispicular, and has two to five spicules adjacent to one another. The amount of collagen is low in both the choanosome and ectosome, mostly concentrated in the nodes joining the spicule tips, acting as a cement to sustain the reticulation. Collagen also bases the Haliclona epithelial layer.